Ethanol Decomposition on Pd–Au Alloy Catalysts

Abstract

The mechanisms of ethanol (EtOH) decomposition via C–C or C–O bond cleavage on alloy surfaces are currently not well understood. In this study, we model EtOH decomposition on close-packed Pd–Au catalytic surfaces using density functional theory (DFT) calculations and derived Bronsted–Evans–Polanyi (BEP) relationships. Three characteristic Pd–Au surfaces are considered, Pd1Au2(111), Pd2Au1(111), and a Pd monolayer (ML), PdML(111), on a Au substrate. We show that, on close-packed Pd–Au surfaces, the C–C bond is easier to cleave than C–O, indicating that the formation of CH4 and CO is favored as the products of EtOH decomposition. Interestingly, we find that, though the C–C and C–O activation barriers on PdML(111) are generally lower than those on the other two surfaces, it is less active for EtOH decomposition due to a slow release of H2 and possible carbon coking. Pd2Au1(111), on the other hand, has a higher theoretical reaction rate due to facile H2 evolution from the surface and less carbon coking. A com...